Why 5000 rpm

O

onadiet

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Jan 1, 2008
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To the guys running big rpm down the track. Help me understand the difference between 30mph wheel speed @ 3000rpm and 30mph wheel speed @ 5000 rpm. Not as hard on drivetrain? Harder on engine?
 
The RPM's keeps you ontop of your turbo and the engine in its power range as the sled will drag the RPM's down toward the end of the track

right?:poke:
 
now I'm not in the truck, but when you listen to a truck running 5000 rpm 5.13 etc. down the track, you hear 5000 to snuff really fast.
 
Maybe I'm being clear enough. Take truck #1, 700hp 30mph wheel speed 3500 rpm maybe 4.10's for conversation. Truck #2 700hp 30mph wheel speed 5000 rpm 5.13's. What truck will do better?
 
Both trucks could do just fine. It depends on the set up. Torque is what tears a motor apart. You want to pull at peak hp and when the sled drags you down at the end it will pull the engine down into the tq. If you try to pull at peak tq at the end of the pull you'll snuff the charger and loose distance. Peak tq is at a lower rpm than peak hp.
 
It seems guys are spending a lot of money for big rpm. If its going to do fine, why spend the money? Everyone else I've talked to says "just cuz."
 
onadiet said:
It seems guys are spending a lot of money for big rpm. If its going to do fine, why spend the money? Everyone else I've talked to says "just cuz."
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mech2161 said:
Both trucks could do just fine. It depends on the set up. Torque is what tears a motor apart. You want to pull at peak hp and when the sled drags you down at the end it will pull the engine down into the tq. If you try to pull at peak tq at the end of the pull you'll snuff the charger and loose distance. Peak tq is at a lower rpm than peak hp.
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I gave you the reason in the above post.
 
I know from my experiance that the higher the rpm the easier it is to get down the track.

Example: My commonrail to get a given wheel speed (say 28 mph) at max rpm stock which is about 3000 i would have to grab a high gear and really abuse the clutch to get the sled going and stay on top of it.

Now say i gain another 1000 rpm. Im able to launch in a lower numerical gear and use the motor to get up to the same wheel speed.

The rpms help when using a larger charger.

Example: On my truck the charger would light at about 2300 rpm. At factory 3000 rpm redline it gives me a very narrow window to keep the charger lit.
Now say a run down the track at 4000 rpm it gives a little more room for error before I get under the charger.

That is just what I saw in my experiance.$.02
 
Torque tears a motor apart. Can you be more specific. I think I'm starting to see the light at the end of the tunnel
 
BGarofalo said:
I know from my experiance that the higher the rpm the easier it is to get down the track.

Example: My commonrail to get a given wheel speed (say 28 mph) at max rpm stock which is about 3000 i would have to grab a high gear and really abuse the clutch to get the sled going and stay on top of it.

Now say i gain another 1000 rpm. Im able to launch in a lower numerical gear and use the motor to get up to the same wheel speed.

The rpms help when using a larger charger.

Example: On my truck the charger would light at about 2300 rpm. At factory 3000 rpm redline it gives me a very narrow window to keep the charger lit.
Now say a run down the track at 4000 rpm it gives a little more room for error before I get under the charger.

That is just what I saw in my experiance.$.02
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That makes sense!
 
When your getting down into peak torque your abusing everything. Your ponding the main bearings, crank, rods, etc. Not to mention the clutch and transmission as well. You get it spinning faster to leseen these forces. You can put 1000 hp through a pencil if its spinning fast enough, but once the torque comes on its toast.
 
onadiet said:
Torque tears a motor apart. Can you be more specific. I think I'm starting to see the light at the end of the tunnel
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Not just the motor the driveline too.

It comes down to how HP is figured.

[(TQxRPM)/5252] = HP

So to make 700 hp at 3000 rpm you need 1226ftlbs of torque

At 5000 RPMyou need 735ftlbs. That is almost 500ftlbs less. Torque is what breaks parts. Horsepower is what pulls the sled.
 
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